Comparative Studies are needed on the biological stage of the bone growth in experimental animals and human to extrapolate the data from animals to For estimating the risk of bone seeking redionuclides in man. The growth of bone length and the appearance and fusion of the secondary ossification centers of seven long bones were compared between both species. The stage of ossification was determined radiographically. The results showed that the ossifying process of the secondary ossification centers could be divided into the following three categories in mice ; (1) acute ossification type, (2) remaining metastable stage type which is specific inmice and generally at the proximal end of bone, and (3) delayed ossification type. Compared with the average life span, differences in ossification between both species were that the appearance of secondary ossification centers was observed within concentrated period in mice and not in man, and that the fusion of these was observed with long duration in mice and not in man. From 17 weeks of age, the metastable status of the bone appeared in mice without complete fusion even at 27 weeks of age, for the experiment with bone seeking radionuclides, mice of age 17 weeks or more should be used consequently

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A congenic strain of mice (DKIR) having a relatively resistant gene for mouse typhoid was established by the beckcross mating between C3H/He and DKI strains. DKI strain is highly and uniformly susceptible to the infection with Salmonella enteritidis and C3H/He is relatively resistant to that infection. The present paper reported the consistency of resistance to Salmonella infection of DKIR strain throughout generations after 10 backcross matings.
Difference of the number of infected organisms in the peritoneal fluid and organs between DKIR and DKI or C3H/He strains was also described. The newly established DKIR strain seems to be a suitable experimental animal for the study of genetical resistance for mouse typhoid when compared with its original DKI strain.

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In a colony of Golden hamsters, many animals were found to show signs, of “wet tail”, and spontaneous deaths occurred during two months. With this outbreak of wet tail and death, etiologic and pathologic studies were made on 11 cases supplied from the colony. Gross pathologic examination disclosed hemorrhagic enteritis in 10 and necrotic foci in the liver in 5 out of 10 cases examined. A number of bacilli morphologically suggestive of Tyzzer's organisms were detected on smears of cut surfaces of the affected intestines and livers. After inoculation with homogenate of the intestines from the moribund cases into hamsters by oral route, the same clinical manifestations as observed in spontaneous cases were reproduced, and the inoculated animals died in 10 to 14 days with numerous Tyzzer's organisms in their intestines and livers. When apparently healthy hamsters were introduced into contaminated cages with soiled bedding which were allowed to stand at room temperature for about 2 months, most of them developed signs of wet tail and died in 5 to 19 days having liver necrosis characteristic of Tyzzer's disease.

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A simple operation method was described for removing the olfactory bulbs of small rodents. The procedure was as follows : 1. Animals were anesthetized by intraperitoneal injection of pentobarbital sodium. 2. The hair of the head was clipped (Fig. 9) . 3. The scalp was cut along the midline between the eyes (Fig. 10) . 4. A hole was drilled in the skull overlying the olfactory bulbs (Fig. 14, 15) . 5. The olfactory bulbs were aspirated with a glass pipette (Fig. 18) . 6. After removing the bulbs by suction, the skin was closed by a single suture (Fig. 21) .

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A micro-agglutination test method for detecting antibodies to Brucella canis was developed. Heat-killed Brucella canis antigens were diluted to an optical density of 0.8 at 420 nm using a spectrophotometer. A volume of 0.025 ml of the antigen was incubated with the same volume of serially diluted sera for 18 to 24 hr at 37 C. Titers of selected dog sera obtained by the present micro-test method were well correlated with the those obtained by the classical tube test with satisfactory reproducibility. The micro-test method is more advantageous for screening the antibodies of dog sera because the test can be performed with : (1) smaller volume of the test sera and the antigen (2) shorter period for incubation, and (3) lesser labor.

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This study was initiated in 1968 with the establishment of a colony of Japanese domestic cat free from intestinal parasites at National Institute of Health of Japan. The purpose of the colony was the production of cats of known genetic background and health status for use in biomedical research. This paper describes the performance of the colony over a 5-year period of continuous breeding. 18 females breeders were divided into three groups according to the time of introduction into colony : 5 females initially were introduced in colony ; 7 females were born in 1973; 6 females were born in 1974. Various aspects of reproductive performance in the cat breeding colony were statistically analysed. Data on reproductive performance was as follows : mean age at 1st parturition was 12 months old ; average interval between parturition was 6 months ; mean litter size was 3.5-4.5 born ; percent weaned was estimated 80 to 90 percent. Difference among queens' groups in the colony has not been found except in mean age at 1st parturition. Influence of queens on mean litter size and percent weaned revealed a significant difference. Influence of litter on percent weaned revealed also a significant difference. Litter size and sex effect on percent weaned revealed non-significant difference. It is possible to conclude that aspects of reproductive performance in our colony was similar to the data reported by other investigators referred to this paper. We hope to set up following aspects of reproductive performance as a goal in 1980: mean age at 1st parturition=10.8 months old ; average interval between parturition=4.8 months ; mean litter size=4.5 ; percent weaned=90 percent.

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The excessive accumulation of gas in the gastrointestinal tracts was invariably induced on experimental animals (mice, rats, guinea pigs, hamsters and rabbits) by simply obstructing nasal passages. The analysis of the gas showed the almost identical composition to the ambient air or f Tutus which was largely due to swallowed air. Also the numerous small foams were found on and underneath the epithelial lining of small intestine. The pathological evaluation was done both macroscopically and microscopically. Dying animals after nasal obstruction showed hemorrhagic and necrotic changes in the jejunum and ileum. This observation may cast some light to the pathogenesis of necrotizing enterocolitis in human neonatal.

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Four hundred and twenty beagles 1 to 4 years of age were examined for spontaneous pathological changes. In the liver were seen fine granular gallstones (87.5%), granulomas (59.9%), intranuclear hyaline inclusions (52.6%), lipofuscin deposition (50%) and eosinophilic inclusions (3.7%) in the cytoplasm of hepatocytes and parenchymal necrosis at the base of the ligaments (7.3%) . Intranuclear hyaline inclusions and lipof uscin deposition were more frequently seen in dogs after being subjected to tests for more than 13 weeks. Besides, hyperplasia of follicular epithelial cells of the thyroid gland (46.3%), Gandy-Gamna like bodies of the splenic capsule (43.1%), small cysts in the anterior lobe of the hypophysis (35.1%) and prostatitis (13.7%) were observed. Lesions due to migration of Toxocara canis larvae were detected in the liver, kidney, lung and other organs from 33.1% of cases examined.

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